Sourcing
How to identify an obsolete or unmarked part
Reviewed August 2026
Short answer
Photograph the part from every angle with a scale reference, record the machine it came from, measure every functional dimension, and note any partial markings, casting numbers or supplier stamps. Those, plus the machine make/model/serial, are enough for a cross-reference search against OEM catalogues, bearing and seal interchange tables, and manufacturer date codes.
Most “impossible to find” parts are found from a good set of photos and measurements plus the machine they came off. Work through this list.
Capture the part
- Photos from six sides, plus close-ups of every marked surface
- A tape measure or scale bar in frame on at least two shots
- Any number, letter, logo, casting mark, forge stamp or date code — even partial
- For bearings and seals: the full number on the race or the seal face
Measure the function
- Every diameter, width, thread, keyway and hole pattern that has to fit something
- Overall envelope dimensions
- For rotating parts: bore, OD, width, and the shaft it runs on
Record the context
- Machine make, model, serial and year
- The assembly the part came from and its neighbours
- What failed and how — it often points to the correct upgraded part
Cross-reference routes
- OEM parts catalogue and supersession notes for the machine serial
- Bearing / seal interchange tables (numbers convert directly across brands)
- Standard-component identification — fasteners, hydraulic fittings, o-rings by dash size
- Local and international suppliers who hold obsolete stock or can remanufacture from a pattern
With that package a supplier can usually come back with a current equivalent, a remanufacture option, or a clear statement of what is still needed to close it out.
Related questions
Very. Casting numbers, forge stamps, patent numbers and supplier codes all feed a cross-reference. Bearings and seals carry their own industry numbers that interchange directly across brands.
